Address Sass deprecation warnings

[raulrpearson]

I got this deprecation warning after a node_modules wipe triggered an asset rebuild, if I'm not mistaken. Notice warnings coming from node_modules/tiny-slider/src/tiny-slider.scss and css/custom.scss. I can reproduce by deleting priv/static/assets/custom.css and re-running the server. Haven't investigated much, just wanted to flag the issue for now.

DEPRECATION WARNING: Using / for division outside of calc() is deprecated and will be removed in Dart Sass 2.0.0.

Recommendation: math.div(100% * $count, $perpage) or calc(100% * $count / $perpage)

More info and automated migrator: https://sass-lang.com/d/slash-div

    ╷
124 │     width: (100% * $count / $perpage);
    │             ^^^^^^^^^^^^^^^^^^^^^^^^
    ╵
    node_modules/tiny-slider/src/tiny-slider.scss 124:13  @import
    css/custom.scss 3:9                                   root stylesheet

DEPRECATION WARNING: Using / for division outside of calc() is deprecated and will be removed in Dart Sass 2.0.0.

Recommendation: math.div(100%, $count) or calc(100% / $count)

More info and automated migrator: https://sass-lang.com/d/slash-div

    ╷
136 │       width: (100% / $count);
    │               ^^^^^^^^^^^^^
    ╵
    node_modules/tiny-slider/src/tiny-slider.scss 136:15  @import
    css/custom.scss 3:9                                   root stylesheet

DEPRECATION WARNING: math.random() will no longer ignore $limit units (60s) in a future release.

Recommendation: math.random(math.div($limit, 1s)) * 1s

To preserve current behavior: math.random(math.div($limit, 1s))

More info: https://sass-lang.com/d/function-units

   ╷
31 │       animation-duration: math.div(random($animationDuration * 10), 10) * 1s + 10s;
   │                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   ╵
    css/custom.scss 31:36  root stylesheet

DEPRECATION WARNING: math.random() will no longer ignore $limit units (16s) in a future release.

Recommendation: math.random(math.div($limit, 1s)) * 1s

To preserve current behavior: math.random(math.div($limit, 1s))

More info: https://sass-lang.com/d/function-units

   ╷
32 │       animation-delay: math.div(random($animationDuration + 10s) * 10, 10) * -1s;
   │                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   ╵
    css/custom.scss 32:33  root stylesheet

Compiled css/custom.scss to ../priv/static/assets/custom.css.